Rheostat



W. SCHWAGERMANN.

'RHEOSTAT.

APPLICATION FILED JUNE 27, 1917.

1,374,241 Patented Apr. 12, 1921.

WILLIAM SGHWAGERMAN'N, or Yomznns,

UNITED s'l A TBS PATENT OFFICE.

NEW Yoax, Assienon 1'0 WARDLEONARD ELECTRIC COMPANY, CORPORATION OF YORK.

To all whom it may concern:

Be it known that I, WILLIAM SCHWAGER- MANN, a citizen of the United States, residing at Yonkers, in the county of West chester and State'of New York, have 1n- A vented certain 'new and useful Improveinexpensive to manufacture. 'All these objects and others will be made apparent in the following specification and claims taken in connection with the accompanying drawings. In these drawings I have shown-one specific device in which my inventive idea may be embodied and I now proceed to describe the particular appanatus shown in the of the contact buttons may be formed drawings.

- Figure 1 is an elevation of my improved rheostat viewed edgewise with respect to the,

plane of the contact buttons; Fig. 2 is a rear elevation of the same;

Fig. 3 is a view of a blank from which one Fig. 4 is a perspective view of a contact blank shown in Fig; 3;

button after it has been shaped from the a Fig. 5 is a view of one of the contact buttons after it has been fixed-to the insulating support therefor; I

Fig. 6 is a corresponding view after the button has been upset according to the method herein described; 7

Fig. 7 is an enlarged fragmental rear ele- #vation showing the resistance elements exposed to view, and

, Fig. 8 is an elevation of apparatus which may be used'to bring the contact buttons inregistry; l

A cast iron disk 11 has a peripheral lip, 12 around the rear face and also has three posts 13 equally spaced around its margin by .which it may be attached to the wall'indicated by the reference'numeral 14. A shaft 15 is rotatably mounted axially with respect to the disk and carries a knob 16 on Patented Apr. 12,. 1921. I Application filed June 2%; 1917. Serial No. 177,245. 5

its outer end by which it may be rotated by hand for adjusting the rheostat. This shaft 15 also carries an index 17 on the outer side of the disk 11, and the rheostat contact arm 18, on the inner side, whose end 37 has a tons '20 in succession.

The back face of the cast iron disk 11 within the rim or flange 12 is coated with a layer of insulating enamel 19 which is member adapted to engage the contact butbaked; then the resistance wire 22 is assemibled with the contact buttons 20 as shown in Fig. 7 and placed on the enamel coat 19,:

Then another coat of enamel 21 is applied which overlies the toes 29 and 30 of the contact-buttons 20, thus supporting them firmly in position. It will be seen that the resistance wire 22 lies between the two enamel coats 19 and 21 and isthus effectively insulated, but at the same time good facility is afforded for dissipating heat from the wire 22 by conduction and radiation.

Insulated binding posts 23 and 24 are provided to which the circuit connections can be made andfrom these one conductor 25.

enamel 19and 21 extends to the insulated -iron disk 341 which lies against the enamel coat 21, and nakesiconductive contact with arm 18.

The contact buttons, each represented generally by the reference numeral 20, are formed from blanks such as shown in F i 3 each cut from suitable'sheet brass. Eac

blank, asshown in ig. .3, has two slots 27 and ismotched near one; end as indicated at 28. I These blanks asshown in Fig. 3 are then given the shape shown in Fig. 4 by which their end portions 29 and 30 lie in the same plane and are adapted to go against the planev surface on which they are to be supported. The extremity of the toe 30 beyond-the notches 28 is bent over andpinched I 29 and 30 and is adapted to be engaged by.

the end of the moving contact arm 18.

After the iron disk 11 has had assembled therewith the two coats of enamel19 and 21 and the resistance elements 22' and the contact buttons 20 it may happen that the outer surfaces 33 of'the contact buttons 20 will not all lie precisely in one plane. One reason Why there may be such deviation would be because the casting 11 may not be perfectly'true; another reason may be that the thickness of the enamel coat, 19 may not be absolutely uniform. Accordingly, I lay the disk 11 down on the anvil 35 and bring the cylindrical die 36 down in engagement with the faces 33 of the contact buttons 20 so as to press all these buttons 20 down from the shape shown in Fig. 5 to that shown in Fig. 6. This brings all the faces 33 in accurate registry in one plane so that the end of the contact arm 18 maysweep smoothly over the buttons 20 in the adjustment of resistance by means of the rheostat.

After the cylindrical die 36 has been pressed down it may be given a slight degree of rotation around its axis by which its lower surface will slightly scratch the surfaces 33 of the buttons 20 in acircumferential direction. Thus, on removal of the die 36, a glance at the buttons 20 will give.-

assurance by the slight scratches that will be shownon the surfaces 33 that the die has indeed engaged all of them andthat they have all been brought into proper registry in a single plane.

The shape of the button, as shown in'Fig. 5, and the formation and location of the slots 27 insure that upon direct pressure against the face 33 the deformation will be as shown in Fig. 6. Also the fact that the slots 27 extend into the, toes 29 and 30 of the button gives a more effective engagement of the enamel coat 21 so that it holds the button more firmly in position.

By turning the handle or knob 16 manually, the arm 18 will be swept over the successive contact buttons 20 passingsmoothly from one to the next and adjusting the .amount of resistance effectively included between the binding posts 23 and 24. 7

Among the advantages of my improvement are that my contact buttons do not require an excessive amount of material, thus avoiding expense for material and my method of bringing their outer surfaces into registry involves no such waste as there would be if they were ground ofl". Also my method of adjustment herein disclosed is very quick and simple and involves small labor cost.

It will be understood that modifications of the foregoing disclosure may bemade that will be included within the scope of my invention.' I

I claim:

1. In the method of adjusting a rheostat so that its arm may smoothly engage the contact buttons in succession, the step which consists in deforming these contact buttons simultaneously and thereby bringlng their surfaces into reglstry.

In the method of adjusting a rheostat so that its arm may smoothly engage the forming the buttons until they are brought into proper registry with one another.

4. In the method of adjusting a rheostat so that its arm may smoothly engage the contact buttons in succession, the steps which consist in deforming these contact buttons simultaneously by the application of a'slngle die and thereby bringing their surfaces into registryand then rotating the die through ace'rtain angleto mark the contact buttons and thereby give indication on removal of the die as.to whether it 'hasQefi'ec tlvely engaged all said buttons.

5. A'rheostat comprising a support, 'arow J of contact buttons carried thereby, resistance elements associated therewith, and an arm adapted to engage said buttons successively, said buttons being of malleable material and deformed so as to bring their surfaces into registry in a single plane for engagement by said arm. Y

6. A rheostat comprisinga support, a row of contact buttons carried'thereby, resistance elements associated therewith, and an arm adapted to engage said buttons successively,

' said buttons being of malleable sheet metal and individually deformed so as to bring their surfaces into registry in a single plane for engagement by said arm. 7

7. A rheostat comprising an iron plate, a

coat of insulating enamel'thereon, a row 0 contact buttons and associated resistance elements mounted on said enamel coat,"an other' enamel coat over said resistance elements and parts of said buttons to retainthem in position, and anarm adapted to engagesaid buttons successively, the/exposed parts of said buttons being of malleable sheetlmetal' and individually deformed after assembly as aforesaid so as to bring their surfaces in accurate registry in one plane to belengaged bysaid arm.

8. A rheostat contact button consisting of a piece of sheet metal with its end portlons lying in a plane and adapted to be'secured to a support and withits intermediate portlon displaced out from the plane of the end portions and-lying'in a parallel plane.

9. A rheostat contact button consisting of a strip of sheet metal with a longitudinal slot cut in each'cnd portion and with its extreme end portions lying in one-plane for of a strip engagement with asupport and its intermediate portion ofiset in aparallel plane.

10. A rheostat contact button consisting of sheet metal with its'two end 1 parts lying in one plane for engagement with a support and one extreme end bent and pinched over a resistance wire, the intermediate part of said strip of metal being ofiset and lying in a parallel plane.

11. in rheostat contact button consisting of a strip of sheet metal with its end portions; lying in a single plane for engagement with support, its middleportion being offwith a support, its middle portion being offthe support.

set in a parallel plane, and the parts joining the portions with the middle portion being curved convexly toward each other and slotted longitudinally.

13. A ,rheostat contact-button consisting of a strip of sheet metal with its end portions lying in a single plane for engagement with'a support, its middle portion being offset in a parallel plane, and the parts joining the end portions with the middle portion being curved convexly toward each other and slotted lon 'tudinally,'the.slotsextend-v ing into the sai end portions.

14. A rheo'stat contact button consistin of a piece of malleable sheet metal having a part adapted to engagea support, a part olfset therefrom, and another part joining them and adapted to be permanently deformed by pressure on the offset part toward 15. A rheostat contact bu'ttbn consisting of a-str1p of sheet metal withvits end portions lying in a single dplane for engagement with a support, its mi dle portion being offset m a parallel plane, and the parts joining the end portions with the middle portion being curved. a a

16. A rheostat contact button consisting buttons. I

6f ma of sheet inetal with its end portions lying in a single lane for engagement with a support, its mi dle portion being offset ina parallel plane, and the parts joining the end portions with the. middle portion being curved-and slottedlong'itudinally, the slots extending into the said end portions, 17. A rheostat. contact button consisting of a strip ofsheet metal with its end portions lying in a single plane for engagement with asupport, its middle portion being ofiset in a parallel plane, and the parts joining the end portions with the middle portion being curved and slotted longitudinally, 18. A rheostat contact button consisting of apiece of malleable metal having a part adapted to engage a support, a part offset therefrom, and another curved part joining them, and adapted to be permanently deformed bypressure on the offset part toward thesu port.

rheostat contact button comprising a .fiat head and an oblique supporting element, the latter being adapted to be ,de-

I formed so asto-bring the head of the button in registry with the heads of other buttons,

20. A rheostat contact button comprising two parallel parts and a connecting" part, one of the parallelparts serving as the contact head, the other parallel part serving for attachment to a support and the connecting partbeing capable of deformation to bring the head in registry with the heads'of other 21. In the method of adjusting a rheostat so that its arm may smoothly engage the contact buttons in succession, the step whlch 1 consists in defprming the most prominent.

buttons at one operation after assembling so as to bring all their contact surfaces in regis- 7 try with the least prominentof them.

22. In the method of adjusting. a rheostat so that its arm may smoothly engage" the contact buttons in succession, the step which consists in deforming themore prominent buttons in proportion to their degree of prominence so as tobring their contact surfaces in're 'stry. I l LIAM SCHWAGERMANN. 

